The Future of Smart Technology

Renewables Are Clean but Carbon-Capture Systems Aren’t

Carbon capture systems used to reduce the amount of CO2 released into the atmosphere are much worse for the environment than renewable sources of energy generation, according to new data.

One of the more piercing arguments against embracing renewable energy is that the production, installation and maintenance of renewable energy generation facilities may cause more CO2 emissions than they are designed to prevent, or worse, have tangential negative impacts on human health and the surrounding ecosystems. Surprisingly little research has focused on either the lifecycles of renewable energy generation facilities, or their total impacts on the environments surrounding them.

“As we move to these new energy systems relying on renewable energies or the capture of CO2 and its storage, we need to ask ourselves what are the benefits and costs and potential risks of such technologies.This is what my team set out to do,” said Edgar Hertwich, professor at the Yale school of Forestry and Environmental Studies and author of a recent study that examined electricity generation from a life cycle perspective. Hertwich said it’s important to make sure that our global transition to renewable energy sources, which he refers to as low-carbon electricity sources, won’t do more harm than good in the long run.

“Low-carbon electricity is really important. Staying within two degrees will require a profound transformation of energy systems,” he said. “Life-cycle assessment hasn’t been used systematically to look at the issue of total benefits and side effects of the technologies.”

The goal: to determine if renewable energy technologies are really as “clean” as their proponents claim them to be.

‘We’ll All Have to Rely on Energy without CO2 Emissions’

Hertwich’s team focused on electricity because it’s one of the main drivers of greenhouse gas emissions. The IPCC (that’s the United Nations’ Intergovernmental Panel on Climate Change) has investigated 1,200 different energy scenarios for the future. The share of low-carbon sources of energy generation increases in all scenarios where global temperatures stay within the two-degree threshold. But we need to increase the share of renewable-generated electricity more quickly in order to ensure global temperatures won’t rise higher than two degrees Celsius above pre-Industrial Era levels. “In the end, we will all have to rely on energy without CO2 emissions in order to stabilize the temperature on the planet,” Hertwich said.

Worldwide electricity generation and efficiency will become important pieces of our global climate change mitigation strategy, he said. That will require an increase in renewable energy sources and increased efforts to capture and store some of the CO2 already in the atmosphere.

For the purposes of the study, Hertwich used a coal-fired power plant to compare results. On average, a coal-fired power plant emits 1 kilogram of CO2 to produce a single kilowatt of electricity. “There is, of course, a range to that, depending on the efficiency of the power plants, the source of the coal that’s being used and how far it has been transported, etc,” Hertwich said.

Most of the emissions are direct emissions from the power plant; there are also some emissions connected to the infrastructure, such as building the power plant, the railways, the transport of the coal; and there are emissions connected to the mining process, and methane escaping from the coal mine.

Not surprisingly, the study found coal-fired power generation contributes the most CO2 emissions. Natural gas, on the other hand, contributes less direct and indirect emissions than coal, but the emissions are still significant. Renewable energy sources such as solar, wind and hydro power also contribute emissions — but to a much less degree than coal or natural gas.

The study looked at PV solar panels, concentrated solar power (CSP), coal and gas with and without CO2 capture and storage, hydro power, geothermal power and wind power. It surveyed damage to ecosystems through pathways such as eco-toxicity, eutrophication, acidification; damage to human health through particulate matter and human toxicity; resource use in terms of major minerals iron, copper, aluminum, cement, and through the use of energy, water and land. The model also took into account associated emissions such as building the required infrastructure and transport of equipment, using database information.

Results: Renewable Energy Is Cleaner than Coal

The main conclusion of the study is that energy generation from renewable sources such as solar, wind and hydro do in fact emit less CO2 and other greenhouse gases into the atmosphere, and that holds true when looking at the entire life of the facility, from construction to decommissioning; and the differences in the amount of emissions when comparing renewable plants and coal or natural gas plants is significant.

“From a life cycle perspective, the GHG emissions from electricity from renewable sources are less than 6% of those generated by coal and less than 10% of those generated by gas power,” Hertwich said. “Solar, wind, hydro, and geothermal power, if it is used instead of fossil fuel power, reduces GHG emissions and other pollution impacts on human health and environmental systems. Impacts are reduced by a factor of three to ten.”

Finally, the study found renewable sources of power generation have less harmful impacts on the environment than traditional coal and natural gas power generation, and these renewable plants have less harmful impacts on human health than coal and natural gas.

Renewable energy sources do require more metals and other raw materials that need to be mined, but Hertwich said that factor doesn’t pose much of a problem. “We will require more materials to implement the climate mitigation scenario than we would continuing on the business as usual path; however the differences are not that dramatic,” Hertwich said. “Most of these materials are actually needed to put in place the low-carbon power infrastructure — they’re not used up in the process, and they can be recycled into new power plants if there is a need for that. The metals we will be able to recycle. Once we’ve built up this stock of materials in the power system, we can use them almost in perpetuity, and that is an attractive feature.”

And Carbon Capture Won’t Cut It

One of the more surprising findings of the Yale study is that the carbon capture systems designed to help reduce the amount of CO2 emissions generated by coal plants actually have negative impacts on other measures of pollution.

“CO2 capture and storage, which is seen as necessary by most of the energy scenarios, can reduce GHG emissions by 50-75% however, at the expense of increasing other types of pollution between 5-80%,” Hertwich said. “We can see that in general the renewable energies have lower impacts and the technologies with CO2 capture and storage have higher impacts. Similar patterns for pollution impacts for ecosystems. There are quite low impacts connected to wind, solar technologies, but there’s an increased impact connected to CO2 capture and storage.”

The bottom line: “Our work quite clearly shows that they [renewables] are a clean source of electricity,” Hertwich said.